Power semiconductor devices, such as those fabricated from SiC (silicon carbide), may be designed to operate at very high operating temperatures (e.g., greater than 250° C.). Such power semiconductor devices may be bonded to a cooling device, such as a heat sink or a liquid cooling assembly, for example. The cooling device removes heat from the power semiconductor device to ensure that it operates at a temperature that is below its maximum operating temperature. The bond layer that bonds the power semiconductor device to the cooling device must be able to withstand the high operating temperatures of the power semiconductor device.
Transient liquid phase (TLP) sintering (TLPS), diffusion bonding, or soldering are methods of high temperature bonding that may be used to bond one substrate to another (e.g., to bond a power semiconductor to a cooling device). For example, TLP bonding results in a bond layer having a high temperature melting point. A typical TLP bond consists of two different material compounds: a metallic layer and an intermetallic layer or alloy. Generally, the intermetallic layer having a high-remelting temperature is formed during an initial melting phase wherein a low melting temperature material, such as tin, diffuses into high melting temperature materials, such as copper, silver, or nickel.
Conventional methods for heating TLP sintered interconnect microstructures have utilized applying force over an entire bonding assembly to form a strengthened bond layer. Such an overall applied force, however, may cause the formation of less voids near edges of the bond layer, resulting in a more dense edge area that may be more susceptible to cracking due to, for example, a coefficient of thermal expansion mismatch between the bond layer and the substrates.
Accordingly, a need exists for alternative methods for heating TLP sintered interconnect microstructures to form a more strengthened bond layer while improving edge compliance to prevent cracking between a pair of substrates.